Polyvinyl alcohol is a synthetic resin prepared by saponifying a polyvinyl ester. It has the feature of being soluble in water and is used for such applications as a raw material for films, an emulsifying dispersant, and an adhesive as well as a raw material for synthetic fibers.
Polyvinyl alcohol is produced by a method in which a saponification reaction feed solution including a polyvinyl ester and an organic solvent is mixed with a saponification catalyst using a rotor mixer or a static mixer, then the mixed liquid is put on a belt type reactor, and a saponification reaction is made to proceed under a predetermined temperature condition. There have heretofore been proposed to use a “static” or “motionless” mixer for preliminary mixing in the saponification of a polyvinyl ester (see Patent Document 1) and to mix a saponification raw solution with a saponification catalyst using a static mixer, then put the mixture on a belt and make a saponification reaction proceed (see Patent Document 2).